Changes in v4:
- Forked off the trivial fixes to skb_frag_t field access to their own
patches and changed this to RFC that depends on these fixes:
https://lore.kernel.org/netdev/[email protected]/T/#u
https://lore.kernel.org/netdev/[email protected]/T/#u
- Use an empty struct for netmem instead of void* __bitwise as that's
not a correct use of __bitwise.
-----------
Changes in v3:
- Replaced the struct netmem union with an opaque netmem_ref type.
- Added func docs to the netmem helpers and type.
- Renamed the skb_frag_t fields since it's no longer a bio_vec
-----------
Changes in v2:
- Reverted changes to the page_pool. The page pool now retains the same
API, so that we don't have to touch many existing drivers. The devmem
TCP series will include the changes to the page pool.
- Addressed comments.
This series is a prerequisite to the devmem TCP series. For a full
snapshot of the code which includes these changes, feel free to check:
https://github.com/mina/linux/commits/tcpdevmem-rfcv5/
-----------
Currently these components in the net stack use the struct page
directly:
1. Drivers.
2. Page pool.
3. skb_frag_t.
To add support for new (non struct page) memory types to the net stack, we
must first abstract the current memory type.
Originally the plan was to reuse struct page* for the new memory types,
and to set the LSB on the page* to indicate it's not really a page.
However, for safe compiler type checking we need to introduce a new type.
struct netmem is introduced to abstract the underlying memory type.
Currently it's a no-op abstraction that is always a struct page underneath.
In parallel there is an undergoing effort to add support for devmem to the
net stack:
https://lore.kernel.org/netdev/[email protected]/
Cc: Jason Gunthorpe <[email protected]>
Cc: Christian König <[email protected]>
Cc: Shakeel Butt <[email protected]>
Cc: Yunsheng Lin <[email protected]>
Cc: Willem de Bruijn <[email protected]>
Mina Almasry (2):
net: introduce abstraction for network memory
net: add netmem to skb_frag_t
include/linux/skbuff.h | 92 +++++++++++++++++++++++++++++-------------
include/net/netmem.h | 41 +++++++++++++++++++
net/core/skbuff.c | 22 +++++++---
net/kcm/kcmsock.c | 9 ++++-
4 files changed, 129 insertions(+), 35 deletions(-)
create mode 100644 include/net/netmem.h
--
2.43.0.472.g3155946c3a-goog
Add the netmem_ref type, an abstraction for network memory.
To add support for new memory types to the net stack, we must first
abstract the current memory type. Currently parts of the net stack
use struct page directly:
- page_pool
- drivers
- skb_frag_t
Originally the plan was to reuse struct page* for the new memory types,
and to set the LSB on the page* to indicate it's not really a page.
However, for compiler type checking we need to introduce a new type.
netmem_ref is introduced to abstract the underlying memory type. Currently
it's a no-op abstraction that is always a struct page underneath. In
parallel there is an undergoing effort to add support for devmem to the
net stack:
https://lore.kernel.org/netdev/[email protected]/
Signed-off-by: Mina Almasry <[email protected]>
---
v4:
- use 'struct netmem;' instead of 'typedef void *__bitwise netmem_ref;'
Using __bitwise with a non-integer type was wrong and triggered many
patchwork bot errors/warnings.
Using an integer type causes the compiler to warn when casting NULL to
the integer type.
Attempt to use an empty struct for our opaque network memory.
v3:
- Modify struct netmem from a union of struct page + new types to an opaque
netmem_ref type. I went with:
+typedef void *__bitwise netmem_ref;
rather than this that Jakub recommended:
+typedef unsigned long __bitwise netmem_ref;
Because with the latter the compiler issues warnings to cast NULL to
netmem_ref. I hope that's ok.
- Add some function docs.
v2:
- Use container_of instead of a type cast (David).
---
include/net/netmem.h | 41 +++++++++++++++++++++++++++++++++++++++++
1 file changed, 41 insertions(+)
create mode 100644 include/net/netmem.h
diff --git a/include/net/netmem.h b/include/net/netmem.h
new file mode 100644
index 000000000000..d821fe0f8147
--- /dev/null
+++ b/include/net/netmem.h
@@ -0,0 +1,41 @@
+/* SPDX-License-Identifier: GPL-2.0
+ *
+ * Network memory
+ *
+ * Author: Mina Almasry <[email protected]>
+ */
+
+#ifndef _NET_NETMEM_H
+#define _NET_NETMEM_H
+
+/**
+ * struct netmem - a nonexistent type marking a reference to generic network
+ * memory.
+ *
+ * A struct netmem* currently is always a reference to a struct page. This
+ * abstraction is introduced so support for new memory types can be added.
+ *
+ * Use the supplied helpers to obtain the underlying memory pointer and fields.
+ */
+struct netmem;
+
+/* This conversion fails (returns NULL) if the struct netmem* is not struct page
+ * backed.
+ *
+ * Currently struct page is the only possible netmem, and this helper never
+ * fails.
+ */
+static inline struct page *netmem_to_page(struct netmem *netmem)
+{
+ return (struct page *)netmem;
+}
+
+/* Converting from page to netmem is always safe, because a page can always be
+ * a netmem.
+ */
+static inline struct netmem *page_to_netmem(struct page *page)
+{
+ return (struct netmem *)page;
+}
+
+#endif /* _NET_NETMEM_H */
--
2.43.0.472.g3155946c3a-goog
Use struct netmem* instead of page in skb_frag_t. Currently struct
netmem* is always a struct page underneath, but the abstraction
allows efforts to add support for skb frags not backed by pages.
There is unfortunately 1 instance where the skb_frag_t is assumed to be
a exactly a bio_vec in kcm. For this case, WARN_ON_ONCE and return error
before doing a cast.
Add skb[_frag]_fill_netmem_*() and skb_add_rx_frag_netmem() helpers so
that the API can be used to create netmem skbs.
Signed-off-by: Mina Almasry <[email protected]>
---
v4:
- Handle error in kcm_write_msgs() instead of only warning (Willem)
v3:
- Renamed the fields in skb_frag_t.
v2:
- Add skb frag filling helpers.
---
include/linux/skbuff.h | 92 +++++++++++++++++++++++++++++-------------
net/core/skbuff.c | 22 +++++++---
net/kcm/kcmsock.c | 9 ++++-
3 files changed, 88 insertions(+), 35 deletions(-)
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index a5ae952454c8..ad2172a889e2 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -37,6 +37,7 @@
#endif
#include <net/net_debug.h>
#include <net/dropreason-core.h>
+#include <net/netmem.h>
/**
* DOC: skb checksums
@@ -359,7 +360,11 @@ extern int sysctl_max_skb_frags;
*/
#define GSO_BY_FRAGS 0xFFFF
-typedef struct bio_vec skb_frag_t;
+typedef struct skb_frag {
+ struct netmem *netmem;
+ unsigned int len;
+ unsigned int offset;
+} skb_frag_t;
/**
* skb_frag_size() - Returns the size of a skb fragment
@@ -367,7 +372,7 @@ typedef struct bio_vec skb_frag_t;
*/
static inline unsigned int skb_frag_size(const skb_frag_t *frag)
{
- return frag->bv_len;
+ return frag->len;
}
/**
@@ -377,7 +382,7 @@ static inline unsigned int skb_frag_size(const skb_frag_t *frag)
*/
static inline void skb_frag_size_set(skb_frag_t *frag, unsigned int size)
{
- frag->bv_len = size;
+ frag->len = size;
}
/**
@@ -387,7 +392,7 @@ static inline void skb_frag_size_set(skb_frag_t *frag, unsigned int size)
*/
static inline void skb_frag_size_add(skb_frag_t *frag, int delta)
{
- frag->bv_len += delta;
+ frag->len += delta;
}
/**
@@ -397,7 +402,7 @@ static inline void skb_frag_size_add(skb_frag_t *frag, int delta)
*/
static inline void skb_frag_size_sub(skb_frag_t *frag, int delta)
{
- frag->bv_len -= delta;
+ frag->len -= delta;
}
/**
@@ -417,7 +422,7 @@ static inline bool skb_frag_must_loop(struct page *p)
* skb_frag_foreach_page - loop over pages in a fragment
*
* @f: skb frag to operate on
- * @f_off: offset from start of f->bv_page
+ * @f_off: offset from start of f->netmem
* @f_len: length from f_off to loop over
* @p: (temp var) current page
* @p_off: (temp var) offset from start of current page,
@@ -2429,22 +2434,37 @@ static inline unsigned int skb_pagelen(const struct sk_buff *skb)
return skb_headlen(skb) + __skb_pagelen(skb);
}
+static inline void skb_frag_fill_netmem_desc(skb_frag_t *frag,
+ struct netmem *netmem, int off,
+ int size)
+{
+ frag->netmem = netmem;
+ frag->offset = off;
+ skb_frag_size_set(frag, size);
+}
+
static inline void skb_frag_fill_page_desc(skb_frag_t *frag,
struct page *page,
int off, int size)
{
- frag->bv_page = page;
- frag->bv_offset = off;
- skb_frag_size_set(frag, size);
+ skb_frag_fill_netmem_desc(frag, page_to_netmem(page), off, size);
+}
+
+static inline void __skb_fill_netmem_desc_noacc(struct skb_shared_info *shinfo,
+ int i, struct netmem *netmem,
+ int off, int size)
+{
+ skb_frag_t *frag = &shinfo->frags[i];
+
+ skb_frag_fill_netmem_desc(frag, netmem, off, size);
}
static inline void __skb_fill_page_desc_noacc(struct skb_shared_info *shinfo,
int i, struct page *page,
int off, int size)
{
- skb_frag_t *frag = &shinfo->frags[i];
-
- skb_frag_fill_page_desc(frag, page, off, size);
+ __skb_fill_netmem_desc_noacc(shinfo, i, page_to_netmem(page), off,
+ size);
}
/**
@@ -2460,10 +2480,10 @@ static inline void skb_len_add(struct sk_buff *skb, int delta)
}
/**
- * __skb_fill_page_desc - initialise a paged fragment in an skb
+ * __skb_fill_netmem_desc - initialise a fragment in an skb
* @skb: buffer containing fragment to be initialised
- * @i: paged fragment index to initialise
- * @page: the page to use for this fragment
+ * @i: fragment index to initialise
+ * @netmem: the netmem to use for this fragment
* @off: the offset to the data with @page
* @size: the length of the data
*
@@ -2472,10 +2492,13 @@ static inline void skb_len_add(struct sk_buff *skb, int delta)
*
* Does not take any additional reference on the fragment.
*/
-static inline void __skb_fill_page_desc(struct sk_buff *skb, int i,
- struct page *page, int off, int size)
+static inline void __skb_fill_netmem_desc(struct sk_buff *skb, int i,
+ struct netmem *netmem, int off,
+ int size)
{
- __skb_fill_page_desc_noacc(skb_shinfo(skb), i, page, off, size);
+ struct page *page = netmem_to_page(netmem);
+
+ __skb_fill_netmem_desc_noacc(skb_shinfo(skb), i, netmem, off, size);
/* Propagate page pfmemalloc to the skb if we can. The problem is
* that not all callers have unique ownership of the page but rely
@@ -2483,7 +2506,21 @@ static inline void __skb_fill_page_desc(struct sk_buff *skb, int i,
*/
page = compound_head(page);
if (page_is_pfmemalloc(page))
- skb->pfmemalloc = true;
+ skb->pfmemalloc = true;
+}
+
+static inline void __skb_fill_page_desc(struct sk_buff *skb, int i,
+ struct page *page, int off, int size)
+{
+ __skb_fill_netmem_desc(skb, i, page_to_netmem(page), off, size);
+}
+
+static inline void skb_fill_netmem_desc(struct sk_buff *skb, int i,
+ struct netmem *netmem, int off,
+ int size)
+{
+ __skb_fill_netmem_desc(skb, i, netmem, off, size);
+ skb_shinfo(skb)->nr_frags = i + 1;
}
/**
@@ -2503,8 +2540,7 @@ static inline void __skb_fill_page_desc(struct sk_buff *skb, int i,
static inline void skb_fill_page_desc(struct sk_buff *skb, int i,
struct page *page, int off, int size)
{
- __skb_fill_page_desc(skb, i, page, off, size);
- skb_shinfo(skb)->nr_frags = i + 1;
+ skb_fill_netmem_desc(skb, i, page_to_netmem(page), off, size);
}
/**
@@ -2530,6 +2566,8 @@ static inline void skb_fill_page_desc_noacc(struct sk_buff *skb, int i,
void skb_add_rx_frag(struct sk_buff *skb, int i, struct page *page, int off,
int size, unsigned int truesize);
+void skb_add_rx_frag_netmem(struct sk_buff *skb, int i, struct netmem *netmem,
+ int off, int size, unsigned int truesize);
void skb_coalesce_rx_frag(struct sk_buff *skb, int i, int size,
unsigned int truesize);
@@ -3378,7 +3416,7 @@ static inline void skb_propagate_pfmemalloc(const struct page *page,
*/
static inline unsigned int skb_frag_off(const skb_frag_t *frag)
{
- return frag->bv_offset;
+ return frag->offset;
}
/**
@@ -3388,7 +3426,7 @@ static inline unsigned int skb_frag_off(const skb_frag_t *frag)
*/
static inline void skb_frag_off_add(skb_frag_t *frag, int delta)
{
- frag->bv_offset += delta;
+ frag->offset += delta;
}
/**
@@ -3398,7 +3436,7 @@ static inline void skb_frag_off_add(skb_frag_t *frag, int delta)
*/
static inline void skb_frag_off_set(skb_frag_t *frag, unsigned int offset)
{
- frag->bv_offset = offset;
+ frag->offset = offset;
}
/**
@@ -3409,7 +3447,7 @@ static inline void skb_frag_off_set(skb_frag_t *frag, unsigned int offset)
static inline void skb_frag_off_copy(skb_frag_t *fragto,
const skb_frag_t *fragfrom)
{
- fragto->bv_offset = fragfrom->bv_offset;
+ fragto->offset = fragfrom->offset;
}
/**
@@ -3420,7 +3458,7 @@ static inline void skb_frag_off_copy(skb_frag_t *fragto,
*/
static inline struct page *skb_frag_page(const skb_frag_t *frag)
{
- return frag->bv_page;
+ return netmem_to_page(frag->netmem);
}
/**
@@ -3524,7 +3562,7 @@ static inline void *skb_frag_address_safe(const skb_frag_t *frag)
static inline void skb_frag_page_copy(skb_frag_t *fragto,
const skb_frag_t *fragfrom)
{
- fragto->bv_page = fragfrom->bv_page;
+ fragto->netmem = fragfrom->netmem;
}
bool skb_page_frag_refill(unsigned int sz, struct page_frag *pfrag, gfp_t prio);
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 12d22c0b8551..4ba626d018e5 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -845,16 +845,24 @@ struct sk_buff *__napi_alloc_skb(struct napi_struct *napi, unsigned int len,
}
EXPORT_SYMBOL(__napi_alloc_skb);
-void skb_add_rx_frag(struct sk_buff *skb, int i, struct page *page, int off,
- int size, unsigned int truesize)
+void skb_add_rx_frag_netmem(struct sk_buff *skb, int i, struct netmem *netmem,
+ int off, int size, unsigned int truesize)
{
DEBUG_NET_WARN_ON_ONCE(size > truesize);
- skb_fill_page_desc(skb, i, page, off, size);
+ skb_fill_netmem_desc(skb, i, netmem, off, size);
skb->len += size;
skb->data_len += size;
skb->truesize += truesize;
}
+EXPORT_SYMBOL(skb_add_rx_frag_netmem);
+
+void skb_add_rx_frag(struct sk_buff *skb, int i, struct page *page, int off,
+ int size, unsigned int truesize)
+{
+ skb_add_rx_frag_netmem(skb, i, page_to_netmem(page), off, size,
+ truesize);
+}
EXPORT_SYMBOL(skb_add_rx_frag);
void skb_coalesce_rx_frag(struct sk_buff *skb, int i, int size,
@@ -1904,10 +1912,11 @@ int skb_copy_ubufs(struct sk_buff *skb, gfp_t gfp_mask)
/* skb frags point to kernel buffers */
for (i = 0; i < new_frags - 1; i++) {
- __skb_fill_page_desc(skb, i, head, 0, psize);
+ __skb_fill_netmem_desc(skb, i, page_to_netmem(head), 0, psize);
head = (struct page *)page_private(head);
}
- __skb_fill_page_desc(skb, new_frags - 1, head, 0, d_off);
+ __skb_fill_netmem_desc(skb, new_frags - 1, page_to_netmem(head), 0,
+ d_off);
skb_shinfo(skb)->nr_frags = new_frags;
release:
@@ -3645,7 +3654,8 @@ skb_zerocopy(struct sk_buff *to, struct sk_buff *from, int len, int hlen)
if (plen) {
page = virt_to_head_page(from->head);
offset = from->data - (unsigned char *)page_address(page);
- __skb_fill_page_desc(to, 0, page, offset, plen);
+ __skb_fill_netmem_desc(to, 0, page_to_netmem(page),
+ offset, plen);
get_page(page);
j = 1;
len -= plen;
diff --git a/net/kcm/kcmsock.c b/net/kcm/kcmsock.c
index 1184d40167b8..145ef22b2b35 100644
--- a/net/kcm/kcmsock.c
+++ b/net/kcm/kcmsock.c
@@ -636,9 +636,14 @@ static int kcm_write_msgs(struct kcm_sock *kcm)
for (i = 0; i < skb_shinfo(skb)->nr_frags; i++)
msize += skb_frag_size(&skb_shinfo(skb)->frags[i]);
+ if (WARN_ON_ONCE(!skb_frag_page(&skb_shinfo(skb)->frags[0]))) {
+ ret = -EINVAL;
+ goto out;
+ }
+
iov_iter_bvec(&msg.msg_iter, ITER_SOURCE,
- skb_shinfo(skb)->frags, skb_shinfo(skb)->nr_frags,
- msize);
+ (const struct bio_vec *)skb_shinfo(skb)->frags,
+ skb_shinfo(skb)->nr_frags, msize);
iov_iter_advance(&msg.msg_iter, txm->frag_offset);
do {
--
2.43.0.472.g3155946c3a-goog
On Tue, Jan 2, 2024 at 1:27 PM Mina Almasry <[email protected]> wrote:
>
> Add the netmem_ref type, an abstraction for network memory.
>
> To add support for new memory types to the net stack, we must first
> abstract the current memory type. Currently parts of the net stack
> use struct page directly:
>
> - page_pool
> - drivers
> - skb_frag_t
>
> Originally the plan was to reuse struct page* for the new memory types,
> and to set the LSB on the page* to indicate it's not really a page.
> However, for compiler type checking we need to introduce a new type.
>
> netmem_ref is introduced to abstract the underlying memory type. Currently
> it's a no-op abstraction that is always a struct page underneath. In
> parallel there is an undergoing effort to add support for devmem to the
> net stack:
>
> https://lore.kernel.org/netdev/[email protected]/
>
> Signed-off-by: Mina Almasry <[email protected]>
>
I think you forgot to update the commit message to replace netmem_ref
with netmem. Also you can mention that you took the approach similar
to 'struct encoded_page'. Otherwise LGTM.
Reviewed-by: Shakeel Butt <[email protected]>